Process for manufacturing oil gas



UNIT n HEATING STEP Jan. 1, 1952 E. L. HALL 2,580,766

PROCESS FOR MANUFACTURING on. GAS

Filed Oct. 1, 1948 I6 TO WASH BOX TO STACK \i TO STACK AI R I mxme ZONE) |X|Ne ZONE) 1/. SOMBLS'LISONI FLUID FUEL ZONE THQT GASES fcAs TO WASH aox UNIT GAS: MAKING STEP l5 6: GAS MAKING OIL +10 STACK l l5 FLUID FuEL-- I HOT GASES GAS TO fwAsu BOX /|2 l0 UNIT IO GAS MAKING STEP GAS MAKING on. ./l4 -9 .GASEOUS DILUENT F l G. INVENTOR I EDWIN L.HALL V BY'HIS ATTORNEY-S Patented Jan. 1, 1952 PROCESS FOR MANUFACTURING OIL GAS Edwin L. Hall, Cleveland Heights, Ohio, asslgnor to American Gas Association, Incorporated, New York, N. Y., a corporation of New York Application October 1, 1948, Serial No. 52,283

8 Claims.

The present invention relates to a novel process for the manufacture of oilgas. and more particularly it relates to an improved process for the manufacture of oil gas by the pyrolysis of petroleum oils inaregenerative-heating operation.

Oil gas has been manufactured for many years by procedures in which petroleum oil is vaporized and pyrolyzed, in the presence of a gaseous diluent such as steam, in zones of stored heat. A zone, or zones, is first heated by burning a fuel and passing the hot products of combustion of the burning fuel therethrough, and, when the zones are sufiiciently heated, oil is then vaporized and, in the presence of a gaseous diluent, pyrolyzed into fixed gases by means of the heat stored in the zone. After-a gas making run, the zone is again heated, followed by another gas making run, and so on. This method ofheating is referred to as cyclic heating as contrasted, for example, to the vaporization of oil in a still where heat is applied continuously to the oil directly from the heat source. In order to pyrolyze the vaporized oil properly not only must the vaporized oil be cracked into molecular fragments, but the cracked materials must be held in a heated zone for a suflicient time for the gaseous system to reach equilibrium during which time the highly reactive molecular fragments become converted into stable molecules of gaseous compounds. To bring this conversion about, the cracked vaporized oil is swept from the initial vaporizing and cracking zone, which is at a relatively high temperature, through a path of stored heat, or fixing zone. The temperatures in the fixing zone must be controlled so that the average temperature thereof is relatively low as compared to that of thecombustion-vaporizing zone where vaporization and initial cracking of the oil takes place, with the highest temperature adjacent the combustion-vaporizing zone and with the temperatures progressively decreasing toward the exit end. By the time the vapors have reached the relatively cooler exit end of this zone, the gas has been fixed and it may then be cooled with the removal of condensable-constituents.

'In the present commercial process, or instance, there is provided a combustion-vaporizing zone, which is often merely the carburetor-generator cell of a carbureted water gas system; and a path of stored heat, or fixing zone, which is often the ,superheater of the carbureted water gas system. The combustion vaporizing zone is merely a chamber providing a space, surrounded by high temperature-resisting walls of heat-conducting material, wherein fuel such-as tar. gas

or oil and air are forced in the proper ratio for combustion, and burned. The hot products of combustion heat the walls of the chamber, and are swept through the superheater where heat is stored in a checkerwork of ceramic material, and thence out the stack. This step is referred to as the blow." Then oil, usually with some steam, is admitted to the combustion-vaporizing zone where the oil is vaporized and cracked, and the mixture is swept through the hot checkerwork where it is fixed into permanent gas, and thence to the wash box. As indicated above, this step is referred to as the gas making run or simply as the make." These steps are repeated continuously as long as required for the gas-making operation. Generally, the apparatus is purged with air or steam between the blow and the make, or between the make and the "blow, or both, to remove undesirable products, to recover the gas remaining in the system and to prevent the accumulation of explosive mixtures. There are various modifications of the commercial process as outlined above, all of which, however, are based on the same sequence of steps.

There are limitations imposed by the above set forth procedure which are becoming presently more serious. In the first place, the present commercial processes can only satisfactorily utilize low residual carbon oils in the gas-making run. For instance, oils containing over 6-'7% free carbon, as determined by the Conradson test more fully described hereinafter, cannot be employed successfully in the gas-making run because of the fact that the carbon deposited on the checkwork in that portion of the fixing zone which is adjacent the combustion-vaporizing zone, will in time clog the system. It has thus been necessary to employ only the low residual carbon oils which are relatively expensive as compared to the more abundant oils containing higher quantities of Conradson carbon, or high residuum oils. A method of manufacturingoil gas wherein high carbon oils may be utilized as the gas-making oil is becoming increasingly desirable with the advent and increasing use of catalyticand thermal cracking techniques in the petroleum refining industry which result in more highly cracked residuum oils which produce much higher ratios of carbon upon gasification. The

- economies of the gas industry require the successassonee a waste since it cannot be utilized in the system but must be removed by periodic cleaning or by intermittent blasts of air or steam. Moreover, as indicated previously, the optimum conditions throughout the system embody a combustionvaporizing zone of relatively high temperature, followed by a fixing zone of relatively low average temperature as compared to that of the combustion-vaporizing zone and in which the temperature progressively decreases toward the exit end. These conditions are met in present day processes only with difficulty since the temperature throughout the system depends for the most part upon the combustion of oil during the blow, and a rate of combustion adapted to provide a relatively high temperature in the combustionvaporizing zone similarly results in undesirably high temperatures in the subsequent path. In other words, the top temperaturelimit in the combustion-vaporizing zone is restricted in order to provide the necessary temperature conditions in the fixing zone. As a result, the temperature in the combustion-vaporizing zone cannot be maintained as high as desirable on the one hand, and the temperature of the fixing zone cannot be maintained as low as desired on the other, and thus a relatively wide temperature gradient between the combustion-vaporizing zone and the exit end of the fixing zone, which would represent the optimum conditions, cannot be obtained economically in present day procedures. This is further aggravated by the fact that the air admitted into the combustion-vaporizing zone during the blow has a cooling effect on that portion of the apparatus which it is desired to have at the highest temperature. All these mentioned limitations. of course, combine to seriously limit the capacity of the apparatus during the gasmaking run. That is to say, since the temperature of the combustion-vaporizing zone, on the one hand, cannot be maintained as high as desired, less eflicient fuel combustion than is possible is obtained during the blow; and since the temperatures in the fixing zone, on the other hand, cannot be maintained as low as desired, less efiicient gasification is obtained during the gas-making run due to over-cracking. Thus, there is room for improvement in the presently practiced procedures with the aim of overcoming the limitations set forth above.

It is, therefore, a principal object of the present invention to provide an economical process for the manufacture of oil gas whereby the aforementioned disadvantages are for the most part overcome or eliminated.

Another object is to provide a process for the manufacture of oil gas wherein there is readily established between the combustion-vaporizing zone and the fixing zone, temperature gradients favorable to the production of the maximum quantity of high heat unit gas per unit of gasmaking oil employed.

Still another object is to provide a process for the manufacture of oil gas whereby heavy residuum and high Conradson carbon oils may be readily employed as gas-making oils.

A further object is to provide a process for the manufacture of oil gas whereby greater efliciency is obtained by the utilization of the carbon deposited in the system during preceding gas-making runs as a part of the fuel required in the subsequent storage of heat in the system.

A further object is to provide a process for the manufacture of oil gas whereby heat losses due to loss of sensible heat in the made gas is kept at a minimum.

Further objects, including the provision of a novel apparatus in which to conduct the process, will be apparent from a consideration of the following specification and the claims.

In accordance with the present invention, there is provided a continuous regenerative process for the manufacture of oil gas by the pyrolysis of petroleum oils in which heat is stored in each of two independently heated interconnected paths each of which is preceded by a combustionvaporizing zone in flow communication therewith, which comprises abstracting a portion of said stored heat from one of said paths by passing air therethrough in the direction of its communicating combustion-vaporizing zone, to raise the temperature of the air and to burn carbon deposited in said path and in said combustionvaporizing zone; admitting the resulting hot gases to the combustion-vaporizing zone preceding the other of said paths of stored heat concurrently with the admission of fluid fuel thereto; burning said fuel in the presence of said hot gases in said combustion-vaporizing zone, the products of said burning being swept through said second mentioned path to store heat therein; admitting petroleum oil to the combustion-vaporizing zone preceding said second mentioned path; vaporing and pyrolyzing said oil in said combustion-vaporizing zone and in said second mentioned path of stored heat; withdrawing said vaporized and pyrolyzed oil from said second mentioned path, and repeating the said sequence of steps with a reversal of the order of said two paths of stored heat. As will be pointed out hereinafter a gaseous diluent is advantageously admitted to the combustion-vaporizing zone concurrently with the petroleum oil during the gasmaking run.

The present invention may be more readily understood by a consideration of the drawings in which Figure 1 illustrates the main steps of a complete cycle of the present process.

It will be noted from the above that in accordance with the present process there is provided a pair of gas-making units, each unit comprising, in flow communication, a combustion-vaporizing zone and a gas-fixing zone. The sequence of steps that occur, i. e. blow and gas-making run in each unit is roughly the same as that occurring in present day procedures, with the exception that air is pased through the fixing zone and combustion-vaporizing zone of one unit from the exit end of the former in the direction of the latter preparatory to its introduction into the combustion-vaporizing zone of the other unit. This exception, however, provides many unexpected advantages as well as fulfilling the objects above. In the first place, by passing air through one unit in the direction stated preparatory to its admission to the other for its blow" or heating step, a wider temperature gradient is provided in the first unit preparing it for its subsequent heating and gas-making runs. In other words, the temperature of the fixing zone of the first unit is materially reduced from a point adjacent to its communicating combustion-vaporizing zone outwardly towards its exit end so that during its subsequent blow" or heating step greater combustion can be had in its communicating combustion-vaporizing zone with consequent higher temperature therein, while still maintaining a relatively low mean temperature in the fixing zone, and with decreasing temperatures from the combustion-vaporizing zone to the exit end of the unit.

Of equal importance, however, is the fact that the air passing through one unit in the direction stated becomes progressively hotter as it approaches the point in the apparatus where carbon deposited from the preceding gas-making run is heaviest. The hot air causes combustion of the previously deposited carbon not only removing it but further raising the temperature of the resulting gases to a high degree just prior to their admission into the combustion-vaporizing zone of the other unit. This not only eliminates cooling, due to the admission of cool air into the combustion-vaporizing zone of the other unit, but also provides more efiicient combustion of the fuel therein. Furthermore, since the hot gases admitted into the combustion-vaporizing zone contains a relatively large amount of sensible heat, both due to the abstraction of heat from the first unit and due to the combustion of carbon deposited therein, a correspondingly less amount of fuel is required for the blow," or heating step, in the second unit. The reduction in the amount of fuel required increases with the amount of carbon deposited by the gas-making oil which is in turn burned during the preheating of the air.

It can thus be seen that-the advantages of the present process are many. Not only can less expensive oil be employed in the gas-making run, but the cheaper the grade employed, i. e. the higher the quantity of carbon it deposits during cracking, the smaller the quantity of fuel required.

It will be also noted from the above that the high temperatures are concentrated in that portion of each unit where they are most necessary, i. e. in the combustion-vaporizing zones, and that portion of the fixing zone immediately adjacent each combustion-vaporizing zone; while lower temperatures are provided where they are most desirable, i. e. in the fixing zone with temperatures progressively decreasing toward the exit end thereof. The net result of this is that more efficient combustion of fuel is obtained in each combustion-vaporizing zone during the particular blow" or heating step of that unit, and more emcient gasification with less overcracking is obtained in each unit during its particular gasmaking run.

Referring more particularly to the drawing, there are shown in Figure 1 two oil gas-making units It) and II each of which is provided with a combustion-vaporizing zone It and I5, respectively, and a path of stored heat, 1. e. fixing zone, l2 and I3 respectively. As seen in 1 which illustrates the heating step for unit ll, there are means for selectively introducing air into the exit end of each unit. One method of doing this is shown in 1 wherein conduits leading to the exit that step. Similarly, I shows one means for selectively withdrawing the materials from the respective units. As shown in 1 there are provided appropriate conduits leading from the exit end of each unit to a conventional two way valve It. By this arrangement gas coming from the respective units may be directed to the wash box,

6 as required. As shown in 1 conventional conduits leading to a stack are also provided. In this case also, the succeeding steps as seen on 1'. 1 and 1 show the direction of flow from the respective. units. There is, of course, conduit means connecting each unit in flow communication from the combustion-vaporizing zone of one to the combustion-vaporizing zone of the other. The direction 01 flow through these means is illustrated in la and 1. Since, for the purposes of the present invention, gas-making unit It may be idle in gas-making step 1", and gas-making unit ll may be idle in gas-making step 1 the representation of gas-making units In and II have been omitted from flow diagrams of steps 1 and 1 respectively in the figure. While each gasmaking unit is illustrated in the figure as a unitary structure, it will be understood that the combustion-vaporizing 'zone of each may be a separate structure or cell, such as a conventional generator-carburetor unit of the type used in present day oil-gas, or carbureted wat'er-gas industries, each of which is in fiow communication with a separate fixing zone such as a conventional super-heater" of the type employed in present day oil-gas or carbureted water-gas industries. Since the figure illustrates the main steps of a complete cycle, it is understood that the system has already been heated to start the process, as is conventional, by burning fiuid fuel such as oil, tar or gas in each combustion-vaporizing zone and blasting the hot combustion gases through the respective fixing zones. Units Ill and H may be connected to a common stack or, as preferred, to separate stacks in order to avoid hot valves, and may be connected either to a common washbox, or to separate wash boxes. Although combustion-vaporizing zones l4 and I5 have been for the purpose of description, illustrated as separate structures. it will be understood that since the conduit means interconnecting them is large so as to handle the hot gas, combustion-vaporizing zones l4 and I5 and the interconnecting con- ISuit means may be developed into a single cham- As shown in 1 of Figure l. the cycle may be started, after each unit has been heated, by passing air through one of the units, in this case unit l0, from the exit end thereof, i. e. the end at which the made oil gas leaves the unit, through the fixing zone I2 and the combustion-vaporizing zone ll respectively. During its passage, the air becomes progressively hotter and at the same time cools the fixing zone l2, by abstracting a portion of the heat stored therein. The hot air causes carbon deposited in unit Ill and especially in combustion-vaporizing zone I and in that portion of the fixing zone I! adjacent combustion-vaporizing zone where the deposited carbon is the heaviest to .burn. Thus, deposited carbon in fixing zone and combustion-vaporizing zone I4 is not only in this way removed but serves as part of the fuel necessary for supplying heat to combustion-vaporizing zone I4 and to The resulting hot mixture of gases is plied to combustion-vaporizing zone I5 if necessary. The'combustion products from combustion-vaporizing zone It are swept through fixing zone 13, storing heat therein. However, since unit II has just previously been swept with air in the same manner as unit III, as described above, relatively large amounts of heat, with correspondingly high temperatures are concentrated in combustion-vaporizing zone It and in that portion of fixing zone It adjacent combustion-vaporizing zone ll, while the temperatures in fixing zone I! rapidly decrease toward its exit end.

The next main step is shown in 1 where gasmaking oil, and advantageously as shown in 1 a gaseous diluent, which is most generally steam, are introduced concurrently into combustionvaporizing zone I! where the oil becomes vaporized and where substantial cracking of the vaporized oil takes place. If desired, oil, or oil and steam may also be added concurrently to combustion-vaporizing zone I of unit l and swept through the conduit means to the combustion vaporizing zone I! of unit H. During this state, the oil is converted into oil-gas constituents, condensable constituents such as tar, dead oil and light oil, and free carbon which latter for the most part is deposited on the walls of the zones and on any checker-work therein. Due to the high temperatures in combustionvaporizing zone IS, a small portion of the steam is decomposed, with carbon in the oil, into water gas,'i. e. hydrogen and carbon monoxide. However, the main function of the steam is to reduce the partial pressure of the gases formed and to serve as a heat transfer medium between the hot surfaces of the zones and the vaporized oil. During its passage through fixing zone l3, the reactive molecular fragments of cracked oil are converted or "fixed into stable molecules of gaseous hydrocarbons. Due to the progressively decreasing temperatures in fixing zone 13 as well as the lower average temperature in zone i3 as compared to that of the fixing zones in conventional processes, the fixation of the gas is facilitated and the danger of over-cracking is reduced. Moreover, for the same reason, the hot gas gives up a portion of its sensible heat to zone l3 which is utilized .in the succeeding steps in preheating air for unit Hi. This means, of course, that the sensible heat recovered in zone I3 is not lost as it is 'in presently practical procedures, and the temperature of the gas leaving zone I3 may be as much as several hundred degrees (Fahrenheit) lower than that of oil gas leaving the fixing zone in presently practiced procedures, and may vary from about 1,000 F. to about 1,400 F.

'The gas produced in unit ll may then be treated by procedures which are well known in the gas-making industry, by being subjected to conventional cooling and condensing operations. Normally. the hot gas is fed to a wash-box which is merely the primary condenser where the gas rs cooled to below the boiling point of water, and condensable constituents such as tar and other hydrocarbons are removed. As stated above, a common wash box advantageously may be employed having a capacity adapted to receive the products from both units.

In Figures 1, 1 and 1 show a repetition of the steps outlined above with a reversal of the order of units. As shown in 1, air is passed through fixing zone l3 and combustion-vaporizing zone l5. As in the previously described steps, carbon deposited during the preceding gas-making run is burned and the hot gases are admitted to combustion-vaporizing zone I4 concurrently with the admission of a fiuid fuel thereto. The fuel is burned in the presence of the hot gases and the combustion products are swept through fixing zone l2, storing heat therein, and thence to the stack. Gas-making oil and diluent are then concurrently admitted to combustion-vaporizing zone H where the oil isvaporized and cracked as described above. The vaporized oil and diluent are swept through fixing zone I! where the gas is fixed and the gas is recovered as also described previously. The process is continued, of course, by repeating the cycle beginning with the step shown in 1.

As indicated above. Figure 1 shows the main steps of the process and it will be understood that suitable purge may be, and advantageously are conducted between one or more of the various steps. For instance, between the steps set forth as 1" and 1 and between 1 and 1, air is advantageously swept through in the direction shown without introducing fuel into the respective combustion-vaporizin zones. This removes from the system undesirable products formed by the combustion of the fuel before the gas-making run is begun. Similarly, between the steps illustrated as 1 and 1 and between steps 1 and 1, a blast of steam is advantageously swept through the respective units in the direction shown to clear the system of oil-gas. In this purging step, there is also advantageously a blast of steam admitted from the exit end of the unit in which oil gas has just been made to insure that no explosive mixtures of gas and air will be obtained when the subsequent "blow," or heating step, is performed.

Referring to the apparatus that may be employed, each part, i. e. the combustion-vaporizing zone and the fixing zone, may be those presently employed in the gas-making industry. As indicated above, the combustion-vaporizing zone may be any of the well known structures used for that purpose, such as the carburetor section of the conventional carbureted water gas apparatus. or one of the combined generator-carburetor structures of conventional oil-gas systems. Specifically, the combustion-vaporizin zone is merely a chamber of heat-conducting material, which is capable of resisting high temperatures, such as clay fire brick, carborundum brick, and the like, designed for the combustion of the fluid heating fuel, and, after it has become sufiiciently heated, for the vaporization of the gas-making oil. The walls of the chamber ordinarily provide sufficient area to store the heat required for the subsequent vaporization and initial cracking of the gas-making oil. The chamber may be completely empty, or may have a portion thereof equipped with checkerwork of ceramic material, such as clay fire brick, carborundum brick, and the like, in which sensible heat may be stored.

As is customary, the combustion-vaporizing zone is provided with a burner adapted to handle the particular fuel employed. Normally, the burner is essentially a jet or jets which inject the fuel into the combustion-vaporizin zone. The burner may be provided with means to mix incoming air with the fuel before it is injected into the combustion-vaporizing zone, or some or all of the air may be separately admitted into the combustion-vaporizing zone. In any event, air and fuel are admitted to the combustion-vaporizing zones in the ratios providing efllcient combustion of fuel therein.

With respect to air passed through one unit preparatory to its admission to the other unit a blast of case the amount of supplemental air required is' correspondingly decreased. Thus, the amount of air passed through the first unit may be sufllcient not only to burn carbon, deposited therein but also to su port the combustion of at least the major portion, and even all of the fluid fuel admitted to the combustion-vaporizing zones.

With respect to the path of stored heat or fixingzone, it may be any of those structures which are well known and are used for that or similar purposes in the oil-gas, or c'arbureted water-gas, industry. It is essentially a large chamber of high temperature-resisting material such as fire brick, the inside of which is provided with many passage Ways through which the gaseous material must flow. Customarily, the inside is provided with a checkerwork of high temperature-resisting material such as clay fire brick with the portion of checkerwork which is to be subjected to the highest temperatures i. e. that portion which is nearest the combustion-vaporiz ing zone, being made of carborundum brick. The fixing zone is of sufficient volume to permit the passing gases to reside there until converted or fixed" into stable oil-gas. The exact size and shape of the fixing zone will be dictated by the considerations well known in the gas-making industry, including capacity desired, requisite holding time, and the like.

Referring to the fuel employed during the "blow or heating step for storing heat in each unit, as indicated previously, it may be any of the fluid fuels ordinarily employed in the gasmaking industry such as petroleum oil, tar, gas, and the like. Generally, the fuel employed will be a petroleum oil and a wide variety of such oils are available for this use such as Numbers 2 and 3 furnace oils, heavy residuum oils, and the like. As stated, tar, such as coal gas tar, carbureted water gas tar, and oil gas tar such as is formed in the process, may also be used as the fuel, in which case it will possess sufllcient fluidity to be handled by the burner and injected into the combustion-vaporizing zone. The proper fluidity may be obtained in some cases by heating the tar, or heavy oil if used, or by thinning them with less viscous miscible liquids of the same nature, or by a combination of these means.

As indicated above, the presentprocess permits the utilization of a wide range of gas-making petroleum oils. Whereas previous processes were restricted to the use of petroleum oils containing less than 7%, and preferably less than 4% Conradson carbon, the present process is readily adapted for the utilization of petroleum oils containing as high as 13% Conradson carbon or even higher. (Conradson carbon is the proportion of carbonaceous residue remainin after a standardized heating cycle is performed on a weighed quantity of the particular oil following the procedure set forth under the A. S. T. M. designation D189-36. In accordance with that procedure, a weighed quantity of oil is heated at a predered heat. From the weight of the carbon re -maining. the Conradson carbon content of that oil is calculated as the P rcentage thereof based on the weight of the 011 sample employed.)

While the process is particularly adapted for the use of oils ranging from the gas-oils or diesel oils through the heavier residuum oils, crude oils and lighter hydrocarbon oils such as propane, butane, kerosene and the like may be employed if desired,

As stated, a gaseous diluent may be, and advantageously is introduced into the combustionvaporizing zone concurrently with the gasmaking oil in order to reduce the partial pressures of the oil vapors. The diluent if used will advantageously condense readily, i. e. at or above the boiling point of water so that at least the major portion thereof may be removed at the wash box. However, condensers having lower temperatures may be employed if necessary.

While steam is the most generally employed diluent, a part or all of the diluent may be hydrocarbon gases which such as methane or other residual gas constituents for the most part'of less than 4 carbon atoms, or water gas. The relative proportions of diluent and gas-making oil may process whether the steam is preheated to supertermined rate in a crucible until a coke-like resi- 1 due is left, and this residue isthen heated to heat in a zone separate and apart from the respective units or whether it becomes superheated during its admission to the combustionvaporizing zone ineach unit and prior to, or during, its commingling with the vaporized gasmaking oil vapors. In copending application of Edwin L. Hall, Serial Number 52,284, filed October 1, 1948, there is disclosed and claimed a process for the manufacture of oil-gas wherein a plurality of independently heated interconnected gas-making units is employed as in the present process, and in which steam is preheated for the gas-making run in one of the units by passing it through the other unit in a direction from the exit end thereof toward the combustion-vaporizing zone thereof. In accordance with the preferred process of said copending application, the cycle is performed by passing air through one unit as described and claimed herein preparatory to its admission to the combustion-vaporizing zone of the other unit, and by preheating steam in one unit preparatory to its admission into the other unit for the gas-making run. The superheating of steam for the gas-making run in one unit by passing it counter-currently through the other unit is not claimed herein but provides the subject matter of said copending application.

The average temperatures in each unit will be similar to those employed during conventional procedures, for example, between about 1150 F. and about 2000" F. and preferably between about 1400 F. and about 1650 F. However, it will be realized that due to the novel procedure herein set forth, relatively higher temperatures, e. g. 100 F. to 500 F. higher, than heretofore will be concentrated at the combustion-vaporizing zones of each unit, while the temperature near the exit end of each fixing zone will be somewhat lower, e. g. 100 F. to 500 F. lower, than those employed in conventional processes.

A series of tests in which air was passed through one unit as described herein before admitting it to the other unit, and this repeated with a reversal of the units, was conducted in which various petroleum oils were employed as the gas-making oil and as the fuel oil. In one test, which lasted several hours, petroleum oil having a Conradson carbon content of 0.20% was employed as gas-making oil and as a fuel oil. In this instance 1.01 gallons of the oil was required as fuel per 1000 cubic feet of gas, and 11.98 gallons of oil was required as gas-making oil per 1000 cubic feet of gas, giving a total of 12.98 gallons of oil required per 1000 cubic feet.

In another test lasting several hours, a petroleum oil having a Conradson carbon content of 6.02% was employed, 0.87 gallon thereof was required as fuel oil per 1000 cubic feet of gas, and 10.76 gallons were required as gas-making oil per 1000 cubic feet of gas, giving a total requirement of oil of 11.63 gallons per 1000 cubic feet of gas. In a third test, lasting several hours, a petroleum oil having a Conradson carbon content of 13.03% was employed as fuel and gas-making oil. Only 0.24 gallon thereof was required as fuel per 1000 cubic feet of gas, and 11.33 gallons were required as gas-making oil per 1000 cubic feet of gas, giving a total oil requirement of 11.57 gallons per 1000 cubic feet of gas. It will be noted, therefore, that not only can high Conradson carbon oils be employed as gas-making oil, but that the higher the Conradson carbon content in the gas-making oil, the less fuel oil is required.

Considerable modification is possible in selecting the various details in practicing the present process without departing from the scope of the invention.

I claim:

1. The process for the manufacture of oil gas by the pyrolysis of petroleum oil in which heat is stored in each of two gas-making units, each of which gas-making units comprises a fixing zone in flow-communication with a combustionvaporizing zone, the combustion-vaporizing zones of said two gas-making units being in flow-communication with each other, which comprises abstracting a portion of said stored heat from the fixing zone and combustion-vaporizing zone of one of said gas-making units by passing air through said fixing zone in the direction of its communicating combustion-vaporizing zone, and thence through said combustion-vaporizing zone, to raise the temperature of the air and to burn carbon deposited in said fixing zone and in said combustion-vaporizing zone; admitting the resulting hot gases to the combustion-vaporizing zone of the other of said gas-making units while burning fluid fuel therein; the resulting hot gaseous products being swept through the fixing zone of said second-mentioned unit to store heat therein; admitting petroleum oil to the combustion-vaporizing zone of said second-mentioned unit; vaporizing and pyrolyzing said 011 in the combustion-vaporizing zone and fixing zone of said second-mentioned unit; withdrawing said vaporized and pyrolyzed oil from said secondmentioned unit; then abstracting a portion of the stored heat from the fixing zone and combustionvaporizing zone of said second-mentioned unit by passing air through said fixing zone in the direction of its communicating combustion-vaporizing zone, and thence through said combustionvaporizing zone, to raise the temperature of the air and to burn carbon deposited in said fixin zone and in said combustion-vaporizing zone; ad-

mitting the resulting hot gases to the combustion-vaporizing zone of said first-mentioned unit while burning fluid fuel therein; the resulting hot a gaseous products being swept through the fixing zone of said first-mentioned unit to store heat therein; admitting petroleum oil to the combustion vaporizing zone of said first-mentioned unit; vaporizing and pyrolyzing said oil in the combustion-vaporizing zone and fixing zone of said firstmentioned unit; withdrawing said vaporized and pyrolyzed oil from said first-mentioned unit; and repeating cyclically said sequence of steps.

2. The process of claim 1 wherein the fluid fuel is petroleum oil.

3. The process of claim 1 wherein the fiuid fuel is tar.

4. The process for the manufacture of oil gas by the pyrolysis of petroleum oil in which heat is stored in each of two gas-making units, each of which gas-making units comprises a fixing zone in flow-communication with a combustionvaporizing zone, the combustion-vaporizing zone of said two gas-making units being in flow-communication with each other, which comprises abstracting a portion of said stored heat from the fixing zone and combustion-vaporizing zone of one of said gas-making units by passing air through said fixing zone in the direction of its communicating combustion-vaporizing zone, and thence through said combustion-vaporizing zone, to raise the temperature of the air and to burn carbon deposited in said fixing zone and in said combustion-vaporizing zone; admitting the resulting hot gases to the combustion-vaporizing zone of the other of said gas-making units while burning fiuid fuel therein, the resulting hot products being swept through the fixing zone of said second-mentioned unit to store heat therein; admitting concurrently petroleum oil and a gaseous diluent to the combustion-vaporizing zone of said second-mentioned unit; vaporizing and pyrolyzing said oil in the presence of said diluent in the combustion vaporizing zone and fixing zone of said second-mentioned unit; withdrawing said vaporized and pyrolyzed oil and diluent from said second-mentioned unit; then abstracting a portion of the stored heat from the fixing zone and combustion-vaporizing zone of said second-mentioned unit by passing air through said fixing zone in the direction of its communicating combustion-vaporizing zone, and thence through said combustion-vaporizing zone, to raise the temperature of the air and to burn carbon deposited in said fixing zone and in said combustion-vaporizing zone; admitting the resulting hot gases to the combustion-vaporizing zone of said firstmentioned unit while burning fiuid fuel therein; the resulting hot gaseous products being swept through the fixing zone of said first-mentioned unit to store heat therein; admitting concurrently petroleum oil and a gaseous diluent to the combustion-vaporizing zone of said first-mentioned unit; vaporizing and pyrolyzing said oil in the presence of said diluent in the combustionvaporizing zone and fixing zone of said firstmentioned unit; withdrawing said vaporized and pyrolyzed oil and diluent from said first-mentioned unit, and repeating cyclically said sequence of steps.

5. The process of claim 4 wherein the fluid fuel is petroleum oil.

6. The process of claim 4 wherein the fluid fuel is tar.

7 14 7. The process of claim 4 wherein the gaseous REFERENCES CITED diluent is steam. The 11 W1 f f 8. The process of claim 4 wherein the fluid fuel file of 33 25 5; erences are 0 record m the is petroleum 011, and wherein the gaseous diluent is steam 5 UNITED STATES PATENTS EDWIN L Number Name Date 2,192,815 Johnson et a1 Mar. 5, 1940 

1. THE PROCESS FOR THE MANUFACTURE OF OIL GAS BY THE PYROLYSIS OF PETROLEUM OIL IN WHICH HEAT, IS STORED IN EACH OF TWO GAS-MAKING UNITS, EACH OF WHICH GAS-MAKING UNITS COMPRISES A FIXING ZONE IN FLOW-COMMUNICATION WITH A COMBUSTIONVAPORIZING ZONE, THE COMBUSTION-VAPORIZING ZONES OF SAID TWO GAS-MAKING UNITS BEING IN FLOW-COMMUNICATION WITH EACH OTHER, WHICH COMPRISES ABSTRACTING A PORTION OF SAID STORED HEAT FROM THE FIXING ZONE AND COMBUSTION-VAPORIZING ZONE OF ONE OF SAID GAS-MAKING UNITS BY PASSING AIR THROUGH SAID FIXING ZONE IN THE DIRECTION OF ITS COMMUNICATING COMBUSTION-VAPORIZING ZONE, AND THENCE THROUGH SAID COMBUSTION-VAPORIZING ZONE, TO RAISE THE TEMPERATURE OF THE AIR AND TO BURN CARBON DEPOSITED IN SAID FIXING ZONE AND IN SAID COMBUSTION-VAPORIZING ZONE; ADMITTING THE RESULTING HOT GASES TO THE COMBUSTION-VAPORIZING ZONE OF THE OTHER OF SAID GAS-MAKING UNITS WHILE BURNING FLUID FUEL THEREIN; THE RESULTING HOT GASEOUS PRODUCTS BEING SWEPT THROUGH THE FIXING ZONE OF SAID SECOND-MENTIONED UNIT TO STORE HEAT THEREIN; ADMITTING PETROLEUM OIL TO THE COMBUSTION-VAPORIZING ZONE OF SAID SECOND-MENTIONED UNIT; VAPORIZING AND PYROLYZING SAID OIL IN THE COMBUSTION-VAPORIZING ZONE AND FIXING ZONE OF SAID SECOND-MENTIONED UNIT; WITHDRAWING SAID VAPORIZED AND PYROLYZED OIL FROM SAID SECONDMENTIONED UNIT; THEN ABSTRACTING A PORTION OF THE STORED HEAT FROM THE FIXING ZONE AND COMBUSTIONVAPORIZING ZONE OF SAID SECOND-MENTIONED UNIT BY PASSING AIR THROUGH SAID FIXING ZONE IN THE DIRECTION OF ITS COMMUNICATING COMBUSTION-VAPORIZING ZONE, AND THENCE THROUGH SAID COMBUSTIONVAPORIZING ZONE, TO RAISE THE TEMPERATURE OF THE AIR AND TO BURN CARBON DEPOSITED IN SAID FIXING ZONE AND IN SAID COMBUSTION-VAPORIZING ZONE; ADMITTING THE RESULTING HOT GASES TO THE COMBUSTION-VAPORIZING ZONE OF SAID FIRST-MENTIONED UNIT WHILE BURNING FLUID FUEL THEREIN; THE RESULTING HOT GASEOUS PRODUCTS BEING SWEPT THROUGH THE FIXING ZONE OF SAID FIRST-MENTIONED UNIT TO STORE HEAT THEREIN; ADMITTING PETROLEUM OIL TO THE COMBUSTION VAPORIZING ZONE OF SAID FIRST-MENTIONED UNIT; VAPORIZING AND PYROLYZING SAID OIL TO THE COMBUSTION-VAPORIZING ZONE AND FIXING ZONE OF SAID FIRSTMENTIONED UNIT; WITHDRAWING SAID VAPORIZED AND PYROLYZED OIL FROM SAID FIRST-MENTIONED UNIT; AND REPEATING CYCLICALLY SAID SEQUENCE OF STEPS. 